The present invention relates to a semiconductor substrate processing method, more specifically to a semiconductor substrate processing method for reducing crystal defects causing device failure.
Semiconductor substrates intrinsically contain various impurities and micro crystal defects caused by the various impurities. As micro crystal defects causing device failure, grown-in defects and micro oxygen precipitates have been recently noted. The grown-in defects are called also LSTDs (Laser Scattering Tomography Defects), COPs (Crystal Originated Particles) and FPDs (Flow Pattern Defects), but these names call the same defects. The defects are void-originated defects surrounded by SiO.sub.2 film.
As semiconductor devices are more integrated, recently device failure caused by micro crystal defects are a serious problem. For improved yields of devices, reduction of such crystal defects is considered very important.
Prior art for reducing such crystal defects are hydrogen annealing and growth of epitaxial layers without defects on surfaces.
In the hydrogen annealing, as shown in FIG. 16 a silicon substrate 100 containing grown-in defects 102 and micro oxygen precipitates 104 is subjected to oxygen out-diffusion annealing in a hydrogen gas ambient. The silicon substrate 100 is subjected to the annealing, e.g., in the hydrogen gas at 1200.degree. C. for about 1 hour. This annealing makes defects 102, 104 near the surface of the silicon substrate 100 smaller, and defects in the substrate surface are reduced. A device is fabricated on the surface of the silicon substrate 100 having defects reduced.
In the growth of an epitaxial layer, as shown in FIG. 17, a defect-free epitaxial layer 106 is grown on the surface of a silicon substrate 100 containing grown-in defects 102 and micro oxygen precipitates 104. A device is fabricated on the defect-free epitaxial layer 106.
In the hydrogen annealing, however, hydrogen gas is used at a high temperature of 1100-1200.degree. C., and it is very dangerous to use the usual furnace. Accordingly, a special apparatus must be used. The universality lack of the apparatus is a problem.
In the growth of an epitaxial layer the growth of an epitaxial layer needs high costs, which makes wafers expensive. This is a problem. For example, an 8-inch wafer with an epitaxial layer formed on has a price even twice that of a usual wafer.